As Kouji continues to fight off Machine Beasts, Dr. Hell sends him a "surprise" in the form of the mechanical life form Kedora, an organism originally made for the Mycenaeans to control their Machine Beasts. As the Kedora takes control of Mazinger, Kouji attempts to stop the rampaging machine and destroy the Kedora itself. After getting help from Nishikiori, Kouji forces the Kedora out of Mazinger, and manages to destroy. Meanwhile, Dr. Hell, Baron Ashura and Viscount Pygman are met by the mysterious Archduke Gorgon.
過去の真相に動揺を隠せない甲児とシロー。解析のために持ち帰った機械獣の残骸の中からミケーネの遺物科学である恐るべき刺客がマジンガーZに襲いかかる!!
从十郎口中得知父亲死因的甲儿同样不愿承认锦织翼是自己的母亲，在母亲苛刻的话语中和士郎一起搬到了光子力研究所，战斗的甲儿越发恼火不顾情况越发疯狂的破坏机械兽，然而除了先生以外没有人注意到有个奇怪的影子蠕动。巴德斯岛里地狱博士发掘了新的秘密——机械生命体-凯德拉。
